N2气氛烧结La掺杂BaTiO3陶瓷的结构与介电性能

采用水热法合成的BaTiO3粉体，分别掺入La(NO)3摩尔分数为0～2．0％，N2气氛1250℃烧结。利用XRD和SEM观测样品的微观结构，用阻抗分析仪测量了在-50～150℃温度范围内样品的介电性能，研究La(NO)3掺杂量对陶瓷样品显微结构和介电性能的影响。试验结果表明：随着La(NO)3掺杂量增大，样品晶粒尺寸逐渐增大。掺杂摩尔分数小于2．0％时，样品主晶相为BaTiO3四方相，介电损耗变化不明显；掺杂摩尔分数大于0．2％时，有第二相Ba5La4Ti8O22存在，介电损耗激增。室温下的表观介电常数ε1呈倒U型变化，当掺杂摩尔分数为0．8％时，室温下ε1达最大值280000。     

掺杂Zn-B-Si-O纳米复合物对BaTiO3陶瓷结构及性能的影响

为了提高BaTiO3陶瓷的介电性能并降低烧结温度,采用溶胶-凝胶法合成的Zn-B-Si-O(ZBSO)纳米复合物和BaTiO3粉体为原料制备了BaTiO3陶瓷.通过XRD,SEM、EDXA和介电性能测试系统研究了ZBSO的煅烧温度、掺杂量和烧结温度对BaTiO3陶瓷的组成,结构和性能的影响.结果表明:ZBSO掺杂量为质...     

工艺对细晶BaTiO_3基陶瓷性能的影响

研究了大容量热稳定细晶BaTiO3基陶瓷的工艺过程,过程一般包括BaTiO3粉料的预处理、混合和烧结等。通过对共沉淀合成的BaTiO3进行热处理,以在1 000℃以上形成四方相;通过对烧结温度,球磨时间,保温时间等因素的严格控制,并且选择恰当的工艺条件,有利于改善系统的介电性能。     

(Mg_(1–x)Zn_x)TiO_3系陶瓷微波介电性能的研究

以MgCO3、ZnO和TiO2为原料,用固相反应法制备了(Mg1–xZnx)TiO3(MZT)系陶瓷。研究了ZnO含量对其微观结构和微波介电性能的影响。结果表明:添加适量ZnO,可有效降低烧结温度,拓宽烧结温度范围。当x(ZnO)为30%,烧结温度为1250℃时,MZT陶瓷具有优良微波介电性能,εr为16～18,Q·f为90000GHz,τc为–5.1×10–7℃–1。     

ZrO_2掺杂BaO-La_2O_3-TiO_2陶瓷预烧温度研究

采用固相反应法,在不同温度(1100~1250℃)下预烧后烧结制备了Ba4La9.33(Ti0.95Zr0.05)18O54微波介质陶瓷,研究了预烧温度对其相组成、显微结构以及微波介电性能的影响。结果表明:不同预烧温度下制备的陶瓷样品主晶相均为类钨青铜结构的BaLa2Ti4O12晶相。1200℃预烧制备的陶瓷样品晶粒为典型的柱状晶,分布均匀,且晶粒尺寸最大。1200℃预烧后,于1400℃烧结制备的陶瓷样品具有最佳的微波介电性能:εr=86.83,Q·f=5875GHz(4.482GHz),τf=81.99×10–6/℃。     

高压烧结的BaTiO3陶瓷的介电性能

用两种高压法烧结得到致密的细晶BaTiO3陶瓷。由压力辅助烧结得到的陶瓷晶粒没有过分长大,晶粒尺寸保持在纳米尺度内;用高压成型常压烧结法得到的陶瓷晶粒明显长大。当BaTiO3陶瓷的晶粒尺寸从400 nm减小到50 nm时,相应的介电常数从3 000减小到1 900。介电常数的减小可由晶粒尺寸的减小而导致四方度的降低和非铁电低介电常数的晶界层解释。且铁电-顺电转变由一个尖锐峰变成一个宽的区域,宽的转变区域表现出扩散相变的特征。     

BST陶瓷制备及介电性能研究

采用微波水热法合成了纳米晶钛酸锶钡(Ba0.6Sr0.4TiO3,简称BST)粉体,并将粉体烧结成陶瓷,对样品的介电性能进行了测试,研究分析了材料的介电性能,并与传统制备工艺获得的样品进行了性能上的对比,实验结果表明:微波水热法获得的BST粉体较细,其合成温度和烧结成瓷温度较传统制备工艺大幅降低,分别为195℃和1 230℃,可以获得晶粒尺寸在3μm以下的陶瓷。随着晶粒的减小,BST陶瓷的相对介电常数和介电损耗降低,尤其是介电损耗因子有较大幅度降低。     

V_2O_5掺杂MgTiO_3-CaTiO_3陶瓷的介电性能

采用固相反应法制备了V2O5掺杂的MgTiO3-CaTiO3(MCT)介质陶瓷。研究了V2O5掺杂量对陶瓷晶相组成、烧结温度和介电性能的影响。结果表明:V2O5掺杂的MCT陶瓷的主晶相为MgTiO3和CaTiO3两相结构,当掺杂量较低时,有第二相CaVO3产生;V2O5掺杂能降低MCT陶瓷的烧结温度并使其介电性能得到改善。当x(V2O5)为1%时,在1250℃烧结2.5h获得最佳性能:εr为20.17,tanδ为2×10–3,αε为4.9×10–5/℃。     

CBS掺杂对钛酸钡陶瓷介电性能的影响

研究了钙硼硅(CBS)微晶玻璃掺杂BaTiO3(BT)-Nb2O5-ZnO系统的微结构和介电性能,并用掺杂后晶粒壳与晶粒芯体积分数的变化规律分析了其改性机理。对比SEM照片得出,不同含量CBS掺杂BT的室温εr与掺杂后BT陶瓷的晶粒生长情况以及玻璃相的多少和分布密切相关。经优化配方和工艺后,在空气中于1150℃烧成的BaTiO3陶瓷材料的主要性能指标达到:εr25℃>1350,tgδ≤1.0×10-2,ρ≥1011?·cm,最大电容量变化率不超过±10%(-55～+150℃),适于制备中温烧结X8R多层陶瓷电容器。     

掺钇(Ba,Sr,Ca)TiO_3纳米粉体及细晶陶瓷的制备与性能

采用sol-gel法制备了Y3+掺杂Ba0.90Sr0.08Ca0.02TiO3(BSCT)纳米粉体及细晶陶瓷。通过TG-DTG、XRD、SEM和TEM对样品结构及形貌进行了表征,并测试了陶瓷的介电性能。研究表明,Y3+掺杂BSCT纳米粉体主要为立方相BaTiO3,烧结后陶瓷晶粒尺寸在0.68~2.24μm可控,Y3+掺杂可以抑制陶瓷晶粒的生长,使陶瓷的tC向低温方向移动。随Y3+掺杂量的增大,陶瓷的介电温谱εr-t趋于平缓,当x(Y3+)为7.0%时,陶瓷的室温εr大幅度提高到9 176。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Call for Papers

正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its